1. Three differences between prokaryotic and eukaryotic cells. The structure and function of organelles common to plant and animal cells. The structure and function of organelles found only in plant cells or only in animal cells.

2. Overview: The Fundamental Units of Life All organisms are made of cells The cell is the simplest collection of matter that can live Cell structure is correlated to cellular function All cells are related by their descent from earlier cells

3. 10 m 1 m 0.1 m 1 cm 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm Atoms Small molecules Lipids Proteins Ribosomes Viruses Smallest bacteria Mitochondrion Nucleus Most bacteria Most plant and animal cells Frog egg Chicken egg Length of some nerve and muscle cells Human height Unaided eye Light microscope Electron microscope

4. (c) Phase-contrast (e) Fluorescence (f) Confocal 50 µm

5. Two basic types of electron microscopes (EMs) are used to study subcellular structures Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3-D Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen TEMs are used mainly to study the internal structure of cells

6. SCANNING ELECTRON MICROSCOPE

9. (a) Scanning electron microscopy (SEM) TECHNIQUERESULTS (b) Transmission electron microscopy (TEM) Cilia Longitudinal section of cilium Cross section of cilium 1 µm

10. 1.Cell fractionation - take apart cells, separate major organelles 2.Ultracentrifuge - applies force 1 million times the force of gravity to separate further the cell organelles with the most dense at the bottom

11. 1.Prokaryotes: Domain Bacteria & Archaea 2.Eukaryotes (Domain Eukarya): Protists, Fungi, Plants, Animals

12. Prokaryotic cells are characterized by having – No nucleus – DNA in an unbound region called the nucleoid – No membrane-bound organelles – Cytoplasm bound by the plasma membrane

13. Prokaryote Vs. Eukaryote “before” “kernel” No nucleus DNA in a nucleoid Cytosol No organelles other than ribosomes Small size Primitive i.e. Bacteria & Archaea “true” “kernel” Has nucleus and nuclear envelope Cytosol Membrane-bound organelles with specialized structure/function Much larger in size More complex i.e. plant/animal cell

14. Concept 6.2: Eukaryotic cells have internal membranes that compartmentalize their functions The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells Protists, fungi, animals, and plants all consist of eukaryotic cells

15. Eukaryotic cells are characterized by having – DNA in a nucleus that is bounded by a membranous nuclear envelope – Membrane-bound organelles – Cytoplasm in the region between the plasma membrane and nucleus Eukaryotic cells are generally much larger than prokaryotic cells

16. Comparing Prokaryotic and Eukaryotic Cells Basic features of all cells: – Plasma membrane – Semifluid substance called cytosol – Chromosomes (carry genes) – Ribosomes (make proteins)

17. The plasma membrane is a selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell The general structure of a biological membrane is a double layer of phospholipids

18. TEM of a plasma membrane (a) (b) Structure of the plasma membrane Outside of cell Inside of cell 0.1 µm Hydrophilic region Hydrophobic region Hydrophilic region PhospholipidProteins Carbohydrate side chain

19. The logistics of carrying out cellular metabolism sets limits on the size of cells The surface area to volume ratio of a cell is critical As the surface area increases by a factor of n 2, the volume increases by a factor of n 3 Small cells have a greater surface area relative to volume

20. Surface area increases while total volume remains constant 5 1 1 6 150750 125 1 6 6 1.2 Total surface area [Sum of the surface areas (height  width) of all boxes sides  number of boxes] Total volume [height  width  length  number of boxes] Surface-to-volume (S-to-V) ratio [surface area ÷ volume]

22. Animal Surface Area Example (Animal): Small Intestine: highly folded surface to increase absorption of nutrients Villi Villi: finger-like projections on SI wall Microvilli Microvilli: projections on each cell

23. Plant Surface Area Example (Plant): Root hairs Root hairs: extensions of root epidermal cells; increase surface area for absorbing water and minerals

25. ENDOPLASMIC RETICULUM (ER) Smooth ERRough ER Flagellum Centrosome CYTOSKELETON: Microfilaments Intermediate filaments Microtubules Microvilli Peroxisome Mitochondrion Lysosome Golgi apparatus Ribosomes Plasma membrane Nuclear envelope Nucleolus Chromatin NUCLEUS

26. Nuclear envelope Nucleolus Chromatin Rough endoplasmic reticulum Smooth endoplasmic reticulum Ribosomes Central vacuole Microfilaments Intermediate filaments Microtubules CYTO- SKELETON Chloroplast Plasmodesmata Wall of adjacent cell Cell wall Plasma membrane Peroxisome Mitochondrion Golgi apparatus

27. The Nucleus: Information Central The nucleus contains most of the cell’s genes The nuclear envelope encloses the nucleus, separating it from the cytoplasm The nuclear membrane is a double membrane; each membrane consists of a lipid bilayer

28. Nucleolus Nucleus Rough ER Nuclear lamina (TEM) Close-up of nuclear envelope 1 µm 0.25 µm Ribosome Pore complex Nuclear pore Outer membrane Inner membrane Nuclear envelope: Chromatin Surface of nuclear envelope Pore complexes (TEM)

29. In the nucleus, DNA and proteins form genetic material called chromatin Chromatin condenses to form discrete chromosomes The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis

30. Ribosomes: Protein Factories Ribosomes are particles made of ribosomal RNA and protein Ribosomes carry out protein synthesis in two locations: – In the cytosol (free ribosomes) – On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)

32. Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell Components of the endomembrane system: – Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane These components are either continuous or connected via transfer by vesicles

33. Smooth ER Nucleus Rough ER Plasma membrane cis Golgi trans Golgi

34. The Endoplasmic Reticulum: Biosynthetic Factory The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER: – Smooth ER, which lacks ribosomes – Rough ER, with ribosomes studding its surface

35. Endoplasmic Reticulum (ER) The Rough ER: package proteins for secretion send transport vesicles to Golgi make replacement membrane

36. Functions of Smooth ER The smooth ER – Synthesizes lipids – Metabolizes carbohydrates – Detoxifies poison – Stores calcium

37. The Golgi apparatus consists of flattened membranous sacs called cisternae Functions of the Golgi apparatus: – Modifies products of the ER – Produce lysosomes – Sorts and packages materials into transport vesicles The Golgi Apparatus: Shipping and Receiving Center

38. cis face (“receiving” side of Golgi apparatus) Cisternae trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus 0.1 µm

39. Lysosomes: Digestive Compartments A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules, or programmed cell death (apoptosis) Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids

42. Food vacuoles are formed by phagocytosis Contractile vacuoles, found in many freshwater protists, pump excess water out of cells Central vacuoles, found in many mature plant cells, hold organic compounds and water

43. Fig. 6-15 Central vacuole Cytosol Central vacuole Nucleus Cell wall Chloroplast 5 µm

44. Concept 6.5: Mitochondria and chloroplasts change energy from one form to another Mitochondria are the sites of cellular respiration, a metabolic process that generates ATP Chloroplasts, found in plants and algae, are the sites of photosynthesis Peroxisomes are oxidative organelles

45. Mitochondria and chloroplasts – Are not part of the endomembrane system – Have a double membrane – Have proteins made by free ribosomes – Contain their own DNA

46. Mitochondria: Chemical Energy Conversion Mitochondria are in nearly all eukaryotic cells They have a smooth outer membrane and an inner membrane folded into cristae The inner membrane creates two compartments: intermembrane space and mitochondrial matrix Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix Cristae present a large surface area for enzymes that synthesize ATP

47. Fig. 6-17 Free ribosomes in the mitochondrial matrix Intermembrane space Outer membrane Inner membrane Cristae Matrix 0.1 µm

50. Chloroplasts: Capture of Light Energy The chloroplast is a member of a family of organelles called plastids Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae

51. Chloroplast structure includes: – Thylakoids, membranous sacs, stacked to form a granum – Stroma, the internal joo-joo

52. Fig. 6-18 Ribosomes Thylakoid Stroma Granum Inner and outer membranes 1 µm

53. Peroxisomes: Oxidation Peroxisomes are specialized metabolic compartments break down fatty acids; detox alcohol Peroxisomes produce hydrogen peroxide (H 2 O 2 ) and convert it to water Oxygen is used to break down different types of molecules

54. Concept 6.6: The cytoskeleton is a network of fibers that organizes structures and activities in the cell The cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell’s structures and activities, anchoring many organelles It is composed of three types of molecular structures: – Microtubules – Microfilaments – Intermediate filaments

55. Fig. 6-21 Vesicle ATP Receptor for motor protein Microtubule of cytoskeleton Motor protein (ATP powered) (a) MicrotubuleVesicles (b) 0.25 µm

56. Components of the Cytoskeleton Three main types of fibers make up the cytoskeleton: – Microtubules are the thickest of the three components of the cytoskeleton – Microfilaments, also called actin filaments, are the thinnest components – Intermediate filaments are fibers with diameters in a middle range

57. Microtubules Microtubules are hollow rods about 25 nm in diameter and about 200 nm to 25 microns long Functions of microtubules: – Shaping the cell – Guiding movement of organelles – Separating chromosomes during cell division

59. Centrosomes and Centrioles In many cells, microtubules grow out from a centrosome near the nucleus The centrosome is a “microtubule-organizing center” In animal cells, the centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring Animal cells

60. Centrosome Microtubule Centrioles 0.25 µm Longitudinal section of one centriole Microtubules Cross section of the other centriole

62. Cilia and Flagella Microtubules control the beating of cilia and flagella, locomotor appendages of some cells Cilia and flagella differ in their beating patterns

63. 5 µm Direction of swimming (a) Motion of flagella Direction of organism’s movement Power strokeRecovery stroke (b) Motion of cilia 15 µm

64. Cross-linking proteins inside outer doublets Anchorage in cell ATP (b) Effect of cross-linking proteins (c) Wavelike motion 13 2

65. Muscle cell Actin filament Myosin filament Myosin arm (a) Myosin motors in muscle cell contraction

66. Intermediate Filaments Intermediate filaments range in diameter from 8–12 nanometers, larger than microfilaments but smaller than microtubules They support cell shape and fix organelles in place Intermediate filaments are more permanent cytoskeleton fixtures than the other two classes

67. Concept 6.7: Extracellular components and connections between cells help coordinate cellular activities Most cells synthesize and secrete materials that are external to the plasma membrane These extracellular structures include: – Cell walls of plants – The extracellular matrix (ECM) of animal cells – Intercellular junctions

68. Cell Walls of Plants The cell wall is an extracellular structure that distinguishes plant cells from animal cells Prokaryotes, fungi, and some protists also have cell walls The cell wall protects the plant cell, maintains its shape, and prevents excessive uptake of water Plant cell walls are made of cellulose fibers embedded in other polysaccharides and protein

69. Plant cell walls may have multiple layers: – Primary cell wall: relatively thin and flexible – Middle lamella: thin layer between primary walls of adjacent cells – Secondary cell wall (in some cells): added between the plasma membrane and the primary cell wall Plasmodesmata are channels between adjacent plant cells

70. Secondary cell wall Primary cell wall Middle lamella Central vacuole Cytosol Plasma membrane Plant cell walls Plasmodesmata 1 µm

71. Functions of the ECM: – Support – Adhesion – Movement – Regulation

72. Intercellular Junctions Neighboring cells in tissues, organs, or organ systems often adhere, interact, and communicate through direct physical contact Intercellular junctions facilitate this contact There are several types of intercellular junctions – Plasmodesmata – Tight junctions – Desmosomes – Gap junctions Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

73. Plasmodesmata in Plant Cells Plasmodesmata are channels that perforate plant cell walls Through plasmodesmata, water and small solutes (and sometimes proteins and RNA) can pass from cell to cell

74. Tight Junctions, Desmosomes, and Gap Junctions in Animal Cells At tight junctions, membranes of neighboring cells are pressed together, preventing leakage of extracellular fluid Desmosomes (anchoring junctions) fasten cells together into strong sheets Gap junctions (communicating junctions) provide cytoplasmic channels between adjacent cells

75. Tight junction 0.5 µm 1 µm Desmosome Gap junction Extracellular matrix 0.1 µm Plasma membranes of adjacent cells Space between cells Gap junctions Desmosome Intermediate filaments Tight junction Tight junctions prevent fluid from moving across a layer of cells

76. The Cell: A Living Unit Greater Than the Sum of Its Parts Cells rely on the integration of structures and organelles in order to function For example, a macrophage’s ability to destroy bacteria involves the whole cell, coordinating components such as the cytoskeleton, lysosomes, and plasma membrane

77. You should now be able to: 1.Distinguish between the following pairs of terms: magnification and resolution; prokaryotic and eukaryotic cell; free and bound ribosomes; smooth and rough ER 2.Describe the structure and function of the components of the endomembrane system 3.Briefly explain the role of mitochondria, chloroplasts, and peroxisomes 4.Describe the functions of the cytoskeleton

78. 5.Compare the structure and functions of microtubules, microfilaments, and intermediate filaments 6.Explain how the ultrastructure of cilia and flagella relate to their functions 7.Describe the structure of a plant cell wall 8.Describe the structure and roles of the extracellular matrix in animal cells 9.Describe four different intercellular junctions